P0420
P0401 P0401
P0455
On-Board Diagnostics
(OBD) Computer
P0128
P0128
P0171
P0171
• Standard in 1996 and later vehicles
• Continually monitors the emissions
control system to maintain proper
engine operation.
OBD Test
• The vehicle’s OBD computer is
connected to the emissions test unit
to directly analyze emissions control
system information.
• During vehicle operation, a Diagnostic
Trouble Code (DTC) is stored in the
onboard computer when an emissionsrelated fault is found. The OBD test can
reveal saved DTCs.
P0300
P0141 P0141
Malfunction Indicator Lamp
(MIL)
• “Service Engine Soon” or “Check
Engine” dashboard panel light
• Illuminates when the vehicle’s OBD
computer detects an emissionsrelated fault.
• Lights up when the vehicle’s emissions
surpass the certification standards by
50 percent.
Benefits of OBD Test
For more
information
call toll-free in
New Jersey:
P0455
YOUR
VEHICLE’S
EMISSIONS
TEST
RESULTS
P0455
888.NJMOTOR
(888-656-6867)
P0455
609.292.6500
• Greater accuracy and faster completion
• Analysis using DTCs aids in identifying problems with your vehicle’s emission
control system for a better diagnosis.
• Immediate detection and correction of
engine fauilts helps avoid expensive
repairs in the future, lowers emissions,
and provides better performance and
fuel economy.
866.337.5669
P0300
P0455
P0128
P0300
Common Diagnostic Trouble Codes (DTCs)
and their causes
P0171/P0174
Exhaust contains
excess oxygen
P0141
Improper operation of
oxygen sensor heater
P0455
Gas cap, lines or
components causing
fuel vapor leak
Readiness and
No Communication
•An OBD test will indicate “Fail for
Communication” if the vehicle’s
OBD system can’t provide data.
•The OBD test will indicate “Fail for
Readiness” if enough monitors have
not executed their checks.
•A monitor is regarded as “Ready”
when it has successfully executed
a check.
P0401
Unsatisfactory
valve/passage
flow in exhaust
gas recirculation
•“Ready” monitors only default to
“Not Ready” when battery power
has been disconnected for repairs
or if the computer memory has
been erased.
Getting Your
Vehicle Ready
•Monitors will generally become
“Ready” after several days of both
city and highway driving.
P0420
Catalytic converter
failing to reduce
emissions
P0300/P0301
Fuel or the ignition system
(spark) possibly causing
engine misfire problems
P0128
Coolant temperature
insufficient (possibly
malfunctioning thermostat)
•After a few minutes of normal
driving, most vehicles without
emissions control system problems
will be “Ready”, but vehicles with
complications may need more time.
•Even when “Ready”, emissions
problems may be detected during
the OBD test, which could return
a failure.